Traditionally, vehicles such as automobiles or the like decelerate by applying brakes limiting the rotation of the vehicle's wheels. The factor limiting the rate of vehicle deceleration is the available tire to road friction, which is a product of tire normal force and friction coefficient. Developments in tires, road services and brakes have sought to optimize the tire-road friction coefficient by utilizing high friction materials, overcoming obstacles such as fluid hydroplaning through tread design, utilizing the advantage of rolling friction over sliding friction by preventing skidding with antilock brakes, utilizing load sensitive and deceleration sensitive proportioning systems to optimize front-to-rear distribution, however, with all these sophisticated advances, deceleration is limited to approximately 1G. There have been sporadic efforts over the years to prove vehicle braking capability by means of increasing the normal loading on the tire as opposed to trying to maximize coefficient friction. Normal loading of the tire is conventionally dependent solely upon the weight of the vehicle. During a deceleration maneuver, there may be a weight transfer to the front wheels, however the total weight remains constant.
One of the most common methods of increasing the
normal load of a vehicle's tires upon the roadway surface is through the use of airfoils and spoilers, as typically seen in racing vehicles. Airfoils work effectively, particularly movable airfoils, at high speeds, but are impractical and ineffective for automobiles operating at typical highway speeds. In order to increase normal vehicle load, several suggestions have been made to employ vacuum-type devices: U.S. Pat. No. 3,167,154--Salvetti suggests the use of a large vacuum chamber attached to the vehicle chassis and shiftable to a road engaging position. U.S. Pat. No. 4,044,862--Savarimuthu suggests the use of suction cups affixed to the vehicle chassis to engage the roadway. U.S. Pat. No. 3,799,293--Howells et al. suggests the use of an auxiliary road engaging friction pad held securely to the roadway by a Rockfield powered jet pump. Others have suggested the use of a vacuum powered anchor or an explosively driven pin which is affixed to the roadway and connected to a vehicle by a cable to increase deceleration rates in emergency situations, as shown in U.S. Pat. Nos. 3,292,738--Bernert et al. and 4,317,507--McMillian.